Filestack is described as 'provides everything a developer needs when working with user content, from connecting to over 15 cloud storage services like Dropbox, Facebook, and Google Drive, to large file uploading directly to S3, to advanced conversion and post-processing functionality' and is an website in the Backup & Sync category. There are more than 10 alternatives to Filestack, not only websites but also apps for a variety of platforms, including Self-Hosted solutions, SaaS, Bitrix24 and PHP. The best alternative is CloudConvert, which is free. Other great sites and apps similar to Filestack are Uppy (Free, Open Source), Uploadcare (Paid), CloudExplorer (Free, Open Source) and Transloadit (Freemium).
Uploadcare handles file uploading, storing, processing, and intelligent delivery via CDN. Save resources spent building the file infrastructure, optimize your content, conversions, load times, traffic, and UX.
Easy File Uploader for your websites in just 1 line of JS code! Supports direct uploading from Facebook, Dropbox, GDrive, via Link, via Image Search, Mic, Camera, Youtube, etc. In built image editor so users can edit, resize, apply filters to images.
Receive print jobs, photos, videos, graphics and other large files on your site. Just copy and paste some HTML to get an upload form that looks like your site. Setup email alerts, password protection and PayPal integration.